package com.lagou.sqlSession;


import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {


    /**
     * 查询
     *
     * @param configuration
     * @param mappedStatement
     * @param params
     * @param <E>
     * @return
     * @throws Exception
     */
    @Override                                                                                //user
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //获取连接并拼装参数的得到PreparedStatement
        PreparedStatement preparedStatement = getPreparedStatement(configuration, mappedStatement, params == null ? null : params[0]);
        //执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        return dealReturnSet(mappedStatement, resultSet);

    }


    /**
     * 更新
     *
     * @param configuration
     * @param ms
     * @param params
     * @return
     * @throws SQLException
     * @throws IllegalAccessException
     * @throws NoSuchFieldException
     * @throws ClassNotFoundException
     */
    @Override
    public int update(Configuration configuration, MappedStatement ms, Object... params) throws SQLException, IllegalAccessException, NoSuchFieldException, ClassNotFoundException {
        PreparedStatement preparedStatement = getPreparedStatement(configuration, ms, params[0]);
        return preparedStatement.executeUpdate();
    }

    private <E> List<E> dealReturnSet(MappedStatement mappedStatement, ResultSet resultSet) throws ClassNotFoundException, SQLException, InstantiationException, IllegalAccessException, IntrospectionException, InvocationTargetException, NoSuchMethodException {
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        // 6. 封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.getDeclaredConstructor().newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {

                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段的值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);


            }
            objects.add(o);

        }
        return (List<E>) objects;
    }

    private PreparedStatement getPreparedStatement(Configuration configuration, MappedStatement mappedStatement, Object param) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql语句 : select * from user where id = #{id} and username = #{username}
        //转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4. 设置参数
        //获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);
        if (isWrapClass(paramtertypeClass)) {
            preparedStatement.setObject(1, param);
        } else {
            List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
            for (int i = 0; i < parameterMappingList.size(); i++) {
                ParameterMapping parameterMapping = parameterMappingList.get(i);
                String content = parameterMapping.getContent();
                //反射
                Field declaredField = paramtertypeClass.getDeclaredField(content);
                //暴力访问
                declaredField.setAccessible(true);
                Object o = declaredField.get(param);
                preparedStatement.setObject(i + 1, o);
            }
        }

        return preparedStatement;
    }


    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if (paramterType != null) {
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;

    }


    public static boolean isWrapClass(Class clz) {
        try {
            return ((Class) clz.getField("TYPE").get(null)).isPrimitive();
        } catch (Exception e) {
            return false;
        }
    }

    /**
     * 完成对#{}的解析工作：1.将#{}使用？进行代替，2.解析出#{}里面的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;

    }


}
